TN 295 
.U4 



No. 9099 






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IC 


9099 



Bureau of Mines Information Circular/1986 



Surface Subsidence Over Longwall Panels 
in the Western United States 

Monitoring Program and Final Results 

at the Price River Coal Co. No. 3 Mine, Utah 



By Alan J. Fejes 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9099 



Surface Subsidence Over Longwall Panels 
in the Western United States 

Monitoring Program and Final Results 

at the Price River Coal Co. No. 3 Mine, Utah 



By Alan J. Fejes 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 







Library of Congress Cataloging in Publication Data: 



Fejes, A. J. (Alan J.) 

Surface subsidence over longwall panels in the Western United 
States: monitoring programs and final results at the Price River Coal 
Co. no. 3 mine, Utah. 



(Information circular; 9099) 
Supt. of Docs, no.: I 28.27:9099. 



1. Mine subsidences -Utah -Price River Watershed. 2. Longwall mining- Utah -Price 
River Watershed. I. Title II. Series: Information circular (United States. Bureau of Mines); 
9099. 



TN295.U4 



[TN319] 



622 s [622'.334] 



86-600182 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Acknowledgments 2 

Price River Coal Co. No. 3 Mine study site 3 

Site selection 3 

Site description 3 

Regional geology 3 

Panel geology 3 

Mine plans 8 

No. 3 Mine 8 

No. 2 Mine 9 

Subsidence-monitoring program 9 

Monument locations 11 

Monument spacing 14 

Monument construction 14 

Monitoring procedures and equipment 15 

Data processing 16 

Subsidence results 16 

Conclusions 18 

References 18 

Appendix. — Measured subsidence values plotted in figures 16, 17, 19, and 20.... 20 

ILLUSTRATIONS 

1 . Project location map 3 

2. Surface contours over longwall panels 4 

3. Typical surface features over longwall panels 5 

4. Regional geologic structures 6 

5. Regional stratigraphy 7 

6. Regional faulting 8 

7. Generalized overburden stratigraphy 9 

8. Price River Coal Co. No. 3 Mine plan 10 

9. Overburden isopachs 11 

10. Royal Coal Co. No. 2 Mine plan 12 

11. Subsidence-monitoring network 13 

12. Access to site limited by heavy snows 14 

13. Monument installation using a sledge hammer 14 

14. Theodolite with electronic distance meter 15 

15. Target-prism unit 15 

16. Final longitudinal subsidence profile for panel 4E 16 

17. Final longitudinal subsidence profile for panel 5E 16 

18. Damage to surface structure located over panel 5E 17 

19. Subsidence development profiles for panel 4E 17 

20. Subsidence development profiles for panel 5E 17 



UNIT 


OF MEASURE ABBREVIATIONS USED 


IN THIS REPORT 


ft 


foot pet 


percent 


in 


inch ppm 


part per million 


in/yr 


inch per year s 


second 



SURFACE SUBSIDENCE OVER LONGWALL PANELS 
IN THE WESTERN UNITED STATES 

Monitoring Program and Final Results 
at the Price River Coal Co. No. 3 Mine, Utah 



By Alan J. Fejes 1 



ABSTRACT 

As part of its mine subsidence research program, the Bureau of Mines 
and the American Electric Power Co. cooperated on a study, conducted at 
the Price River Coal Co. No. 3 Mine, directed toward developing the 
capability to estimate the surface subsidence resulting from longwall 
mining in a geologic, topographic, and mining environment common to 
coalfields in the Western United States. 

Subsidence was monitored at the No. 3 Mine over two adjacent longwall 
panels. The subsidence study area was reduced when the two planned 
panels were reduced in length because of equipment failure and a mine 
fire. Subsidence was measured for 21 months. Subsidence continued for 
6 months after mining had been completed. A maximum of 2.2 ft of sub- 
sidence occurred over the two longwall panels rained at an overburden 
depth ranging from 300 to 1,500 ft. 

'Mining engineer, Denver Research Center, Bureau of Mines, Denver, CO. 



INTRODUCTION 



In 1977, Congress passed the Surface 
Mining Control and Reclamation Act. Sec- 
tion 516 (5) (1) of the act requires the 
mine operator to "...adopt measures... 
to prevent subsidence causing material 
damage...." A method of predicting the 
approximate location and magnitude of 
subsidence is necessary to prevent or 
limit subsidence-related material damage. 
These methods are currently unavailable 
or inadequate for U.S. mining conditions. 
To expand prediction capabilities, a more 
inclusive subsidence data base must be 
developed. A more expansive data base 
would provide researchers and mine opera- 
tors with the information required to 
delineate the individual and combined 
effects of the many mining and geolog- 
ic parameters that contribute to mine 
subsidence. 

In the United States, approximately 40 
million acres are subject to subsidence 
from past, present, and future coal min- 
ing. Only 8 million acres of this total 
area had been undermined prior to 1977 
( 1) . 2 Monitoring subsidence over the re- 
maining 32 million acres would be im- 
practical and uneconomical; therefore, 
a system of selective monitoring is re- 
quired to effectively and efficiently 
characterize mine subsidence to help de- 
velop subsidence prediction methods that 
can be used to limit the amount of damage 
to these remaining unmined lands. The 
first step in this characterization pro- 
cess is to select and systematically 
monitor representative sites in actively 
mined coalfields. Comparison and analy- 
sis of collected data will determine the 
affects and significance of individual 
mining and geologic parameters for each 



coalfield. The number of sites required 
for each coalfield will depend upon the 
consistency of collected subsidence data 
and the accuracy required for the predic- 
tion methods. 

In the Western United States, very 
little subsidence information is availa- 
ble for mine operators. Therefore, there 
is little data to correlate with data 
from other sections of the United States 
or other countries to determine the ap- 
plicability of existing subsidence pre- 
diction methods. The Bureau is especial- 
ly interested in western coalfields where 
a significant number of underground coal 
mines operate under Federal coal leases 
and therefore undermine public lands. 

The Bureau's subsidence research pro- 
gram promotes maximum utilization of both 
underground and surface natural resources 
by supporting the development of subsid- 
ence prediction methods. The ability to 
predict subsidence enables mine opera- 
tors to use high-extraction mining meth- 
ods, to maximize recovery and control 
subsidence, thereby avoiding or limiting 
surface and subsurface subsidence 
damage. 

The Rocky Mountain Coal Region site 
was established in cooperation with the 
American Electric Power Co. at the Price 
River Coal Co. No. 3 Mine in Carbon 
County, UT. The major objectives of the 
Price River study were as follows: 

1. Measure surface subsidence caused 
by longwall mining in the Spring Canyon 
Sub 3 Seam coalbed. 

2. Establish the final longitudinal 
subsidence profiles. 

3. Determine the effects of subsid- 
ence on current and potential land use. 



ACKNOWLEDGMENTS 



The Price River Coal Co. provided val- 
uable assistance in conducting this 

^Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendix. 



research. In particular, Laine Adair, 
Ken Hutchinson, and Ace Muse have made 
significant contributions to the project. 
Without the access that was provided 
to company property, mine plans, survey 



data, drill logs, and other informa- 
tion relating to the Price River Coal 



Co. No. 3 Mine, this 
have been conducted. 



PRICE RIVER COAL CO. NO. 3 MINE STUDY SITE 



study could not 



SITE SELECTION 

The Price River Coal Co. No. 3 Mine is 
situated in the Book Cliffs Coalfield; 
historically, the most productive coal- 
field in Utah. Production in 1981, from 
six underground coal mines in the Book 
Cliffs Coalfield, was 3.36 million short 
tons. Remaining recoverable reserves for 
the field are estimated at 1.4 billion 
short tons. (2). The geological and geo- 
graphical features of this site are typ- 
ical for western underground coal mines. 
The terrain is rugged and the over- 
burden contains a high percentage of 
strong sandstone strata. The results of 
this study are expected to be applicable 
to other sites within the Book Cliffs 
Coalfield and possibly to other western 
region coal mines. 

SITE DESCRIPTION 

The study site over the No. 3 Mine 
is located in Bear Canyon in Carbon 
County, UT, approximately 5 miles north- 
west of the town of Helper. The site 
includes parts of Sec. 34 and 35, T 12 S, 
R 9 E on the Standardville 7.5-min- 
ute U.S. Geological Survey quadrangle 
map (3). The project site location is 
illustrated in figure 1. The study site 
is approximately 300 acres within the 






Q^® 




1 


Price River \ 




I 


Coal Co. V, 




N 

1 


Study sire ft / 

is \y 

'"- — ^Sgrjng ^ 
Condon c 


/Helper 




■7. U 

<> 


^ Price 



FIGURE 1.— Project location map. 



Price River Resource Area. This area 
is managed by the U.S. Bureau of Land 
Management. 

The topography over the study area is 
extremely rugged with steep slopes, sheer 
cliffs, and numerous sandstone outcrops 
(figs. 2-3). Elevation at the site 
ranges from approximately 6,500 to 7,200 
ft, and vegetation consists of sagebrush, 
scrub oak, and evergreens (fig. 3). The 
study area has a semiarid climate, with 
an average rainfall of 15.25 in. Most 
precipitation falls in the winter months 
in the form of snow, an average of 107 
in/yr (4_). 

REGIONAL GEOLOGY 

The No. 3 Mine is located in the Spring 
Canyon Sub 3 Seam coalbed in central 
Utah, which is part of the Book Cliffs 
Coalfield (fig. 4). This field marks the 
southern border of the Uinta Basin (_5 ) . 
The overburden is composed primarily of 
sedimentary rocks with a regional dip 
averaging 5° northward. The overburden 
is composed of sandstone, shale, carbona- 
ceous shale, and coal. The rocks within 
the coalfield are subdivided into five 
formations (fig. 5). Ages of these rocks 
vary from upper Cretaceous to Tertiary. 

Figure 6 illustrates faulting within 
the Book Cliffs Coalfield (5)» Faulting 
is a significant problem for some mines 
in this area; displacements along major 
faults can range from 10 to 200 ft. How- 
ever, the Price River Coal Co. No. 3 Mine 
is relatively unaffected by faulting. 
The faults that do intersect the mine 
are considered insignificant since they 
only create small displacements that do 
not inhibit mining operations. 

PANEL GEOLOGY 

The No. 3 Mine produces coal from the 
Spring Canyon Sub 3 Seam coalbed in 
the coal-bearing zone of the Blackhawk 
Formation. This formation consists of 




6 Bureau control points 

° Bureau subsidence monuments 

FIGURE 2. — Surface contours over longwall panels. The subsidence monitoring network, shown as lines of circles, is discussed 
in the section "Monument locations." 



slope-forming siltstones and shales and 
cliff-forming sandstones. The major 
coalbeds occur in the lower 
this formation. 

The Spring Canyon Sub 3 
has an average thickness of 
the study panels. The coal 
as hard, bright, and dense, and is ranked 
as high-volatile, A bituminous. 

An analysis of drill-hole records, sup- 
plied by the Price River Coal Co. , was 
used to determine the stratigraphy of 
the overburden above the longwall mining 



one-third of 

Seam coalbed 

6 ft within 

is described 



operation. A generalized overburden 
stratigraphic column is shown on figure 
7. The major unit in this column is the 
Castlegate sandstone. 

The Castlegate sandstone is located in 
the lower Price River Formation and is 
described by Doelling (_5) as a gray, 
fine- to medium-grained, massive sand- 
stone with occasional shale and coal 
partings occurring in the lower portion 
of the unit. Over the panels the sand- 
stone is approximately 500 ft thick. 




FIGURE 3.— Typical surface features over longwall panels. 




M 



/Book Cliffs 
Coalfield 



INDEX MAP 





L 



-N- 



25 



50 



Scale, miles 



FIGURE 4.— Regional geologic structures. 



T3 
O 


o 


STRATI GRAPHIC 


THICKNESS, 


DESCRIPTION 


o> 


o 
o. 


UNIT 


ft 




Q_ 


UJ 








Ter 


tiary 


NORTH HORN 
Formation 


350- 
2,500 


Gray, calcareous, and silty shale, tan, fine- 
grained sandstone; and minor conglomerate. 

Unit thickens to west. 








E 






Yellow-gray medium-grained sandstone and 








> 

or 


Upper 


500- 
1,500 


shaly sandstone with gray shale. Unit 
thickens along east edge of field. 






Gray, fine- to medium-grained, argillaceous 








o 


Castlegate 


100- 


massive, resistant sandstone thinning east- 






O 

o 


0- 


S.S. 


500 


wardly with subordinate shale. 








Cyclical littoral and lagoonal deposits 




</> 










with 6 major cycles. Littoral deposits of 




3 
O 


■o 


E 






mainly massive cliff-forming, gray fine- 




a> 
o 
o 

•»- 


a> 








to medium-grained sandstone; individual 




> 
o 


o 


Upper 


600- 
1,100 


beds separated by gray shale. Lagoonal 
facies consist of thin- to thick-bedded 


v> 

3 


o 


5 






gray sandstones, shaly sandstones, shale, 






o 
o 






and coal. Coalbeds form basis of Book 


O 

0) 






m 






Cliffs Coalfield. Unit thins eastward 


o 

o 

■*- 

OJ 

w- 
O 


Q. 

a. 

3 






Aberdeen Member}- 




grading into the Mancos Shale. 


CO 

to 


S? rina Member? 
Canyon j — 












-♦- 


^^. 




Yellow-gray, massive, medium- to fine- 








c 

o 
0_ 

o 


Storrs ~"^n 


0- 


grained littoral sandstone tongues pro- 








To ng u e ^ -J 


580 


jecting easterly, separated by gray 
marine shale tongues projecting westerly. 








CO 


Panther"? 
Tongue i^ 












■Gray marine shale, nonresistant , form- 








Ma us k 




ing flat desert surfaces and rounded 






w 

o 

c 

CO 


Shale 


4,300- 
5,050 


hills and badlands. Separated mainly 
to the west into tongues by westward 
projecting littoral sandstone that 


Emery S.S^""^"" 
Member^" 






o 


eventually grades into shale. Sand- 










stones are fine- to medium-grained, 






u 

c 






yellow-gray to tan, and medium-bedded 






o 

2 


Bluegate Shale 




to massive and cliff forming. 



FIGURE 5.— Regional stratigraphy (modified from Doelling, pp. 251, 267). 




FIGURE 6.— Regional faulting (modified from Doelling, pp. 252-253). 



MINE PLANS 

The subsidence study site is located 
over multiple-seam mining. In addition 
to the Spring Canyon Sub 3 Seam coalbed 
being mined by the Price River Coal Co. 
in the No. 3 Mine, an upper bed was mined 
by the Royal Coal Co. in its No. 2 Mine. 
The abandoned No. 2 Mine, operated in 
the 1940's, lies approximately 430 ft 
above the No. 3 Mine. A description 
of each mine plan is included in this 
section. 

No. 3 Mine 

The mine plan for the No. 3 Mine is 
shown in figure 8. The study area con- 
sists of two adjacent longwall panels 
oriented on a bearing of N 75° 26 f 12" E 
to be retreat mined from east to west. 



Two longwall panels (2E and 3E) south 
of the two study panels (4E and 5E) 
were mined prior to the study. The 
development entries for panels 2E and 
3E had three three-entry systems with 
cross-cuts on 105-ft centers; entry 2-1/2 
East on a 70-ft center, 3rd East was on 
a 60-ft center, and 4th East was on 
a 50-ft center. The face lengths of 
panels 2E and 3E are 500 ft each, 
with lengths of 2,000 and 2,420 ft, 
respectively. 

The 5th and 6th East development en- 
tries for panels 4E and 5E were driven 
on 50-ft centers; crosscuts were driven 
on 105-ft centers. Panel 4E was 1,550 
ft long with a face length of 450 ft; 
panel 5E was 1,950 ft long with a face 
length of 500 ft. 



0- 


,V ° ° 
\o V 


300- 
350- 
400- 
450- 
500- 
550- 
600- 

























50- 









*> ~ ■ 






M^M 

















100- 








- — ' 



























;■'.;■. v'r .•■'.-' 














— — 












150— 


SHVM 


















- ~ T" 
















200- 


■•: ■'•'::'' 


J*. . *> 


















3^E 












250- 


• • 












— 










— 






— =— 



















300- 


'.•'.'. :.■■-■'.' 


1 



600 



650- 



700- 



750- 



800- 
81 



.WAfri j 



tm* 



Castlegate 
Sandstone 



Spring Canyon 
Sub 3 Seam 



LEGEND 
I*. ■■"'■I Alluvium 

] Sandstone 
IsKBI Shale 



Interbeds ot sandstone 
and shale 



| — _-| Carbonaceous 



Coal 



FIGURE 7.— Generalized overburden stratigraphy. 

The depth of cover over panel 4E ranges 
from 800 to 1,500 ft; over panel 5E the 
cover ranges from 800 to 1,200 ft. The 
minimum overburden for panels 4E and 5E 
occurs near the center of the panels and 
increases toward both ends (fig. 9). The 
seam dips 9° on a strike of N 10° E, 
which was considered when calculating 
overburden depths. 

Panels 4E and 5E were only partially 
mined because of mining problems. Mining 
in panel 4E was discontinued when the 
longwall equipment failed. The longwall 



equipment was removed and a new longwall 
system was installed in panel 5E . While 
installing the new longwall, the coal 
remaining in panel 4E was partially room- 
and-pillar mined directly behind the 
abandoned longwall face. 

Panel 5E was abandoned when a fire was 
detected. The fire was believed to be in 
the room-and-pillar section located be- 
hind the 4E longwall face. Panels 2E , 
3E , 4E , 5E , and 6E were sealed to contain 
the fire. 

No. 2 Mine 

The mining plan for the Royal Coal Co. 
No. 2 Mine (also known as the Cameron 
Mine) is shown in figure 10. The plan is 
included in this report to show that the 
study area was not located in a virgin 
area and may have affected subsidence 
values (6_). The mine is in the Castle- 
gate "D" (Kenilworth) bed, approximately 
430 ft above the Sub 3 Seam coalbed. The 
No. 2 Mine was opened in 1912 and was 
actively mined until the workings were 
abandoned in 1962. The mining height 
within the study area ranged from 6 to 8 
ft. The coal within the study area was 
mined between 1946 and 1949. 

The Castlegate "D" coalbed was worked 
using standard room-and-pillar mining 
methods with pillars pulled in isolated, 
seemingly random sections. The extrac- 
tion ratio in the section above panel 4E 
is 0.28; above panel 5E the ratio is 
0.43. The positions of panels 4E and 5E 
relative to the old workings are shown on 
figure 10. 



SUBSIDENCE-MONITORING PROGRAM 



Figure 11 shows the subsidence-monitor- 
ing network located over two adjacent 
longwall panels at the No. 3 Mine. The 
network was designed to measure the max- 
imum subsidence, the longitudinal subsid- 
ence profiles, and the rate at which 
subsidence progresses over the longwall 
panels. 



Major items that affected collected 
subsidence data included survey accuracy 
and frequency, monument spacing, monument 
construction, and surveying instrumenta- 
tion. The number and accuracy of sur- 
veys performed was affected by climatic 
and geographic conditions at the site. 
Heavy winter snows usually made the site 



10 







7tt> Eo«t N 75 26' 12 E 



V t- . : •""^gaDDDDDDDDDDDDDDDDQDDDDDaQaaaCDril Cl 

* * i . "H-" : r :. jgD DDDDaDDD D QQDg ggggs5g"oggpogpL '-*30Q< 

f '' - ' ** jr Panel 6E DDL 

oop 

cor 

' ' •' j I - ^V 1 •* EG,f <> D ! 

A %**■% ]|_ JFS? ^_ . .._ _ ___.__., ■*•!■* 5 DC 

i l T ioor 




FIGURE 8.— Price River Coal Co. No. 3 Mine plan. 



11 




FIGURE 9.— Overburden isopachs. 



inaccessible from November into May (fig. 
12), which prevented the Bureau from 
performing surveys at regular intervals 
throughout the year. Installation and 
monitoring of the network in the rugged 
terrain was physically intensive and time 
consuming. 

MONUMENT LOCATIONS 

The locations of the subsidence monu- 
ments were established from coordinates 
supplied by the Price River Coal Co. for 
surface control points in or near the 
study site and underground points on the 
longwall panel boundaries. All surface 
and underground surveys were tied to the 
Utah State Plane Coordinate System, which 
allowed direct correlation between sur- 
face and underground positions. 

The network layout consisted of two 
lines of monuments centered on the longi- 
tudinal axis of each panel. A transverse 
line of monuments was installed across 



panels 4E and 5E. However, mining in the 
two panels did not progress close enough 
to this monument line to cause it to 
subside. Had the entire lengths of the 
panels been mined as planned, the trans- 
verse monitoring line would have been 
located in the area of maximum subsid- 
ence. Because the line was outside the 
area of subsidence influence, no data 
were obtained. 

The location of stable control points 
was governed by the topography and vege- 
tation of the site and the location 
of underground workings. Five control 
points were established to monitor the 
entire network. One control point was 
located within the influence of subsid- 
ence to provide a line of sight to 
several particularly isolated subsidence 
monuments. This control point was tied 
to two stable control points prior to 
each survey of the network to ensure 
accuracy. 



12 













Scale, ft 



FIGURE 10.— Royal Coal Co. No. 2 Mine plan. 



13 




jf }* X, ,• ■■' ! r ,'i •: -Vi., ](__ 71* Eoi» N 73* 26' 12" E 

'■ * / ' r " ' : - ;!<; ';6QDDDDDDDaDaDDDDDDaDDDaaabaacDLDC]f -JwoDoa 



* '* At • - L 



• / * 



Panel 6E |00| 

::lMt. Barrier 005/ 

oof 

or 
+ + + +++'+++ + + + +++++ + + + +++ -KM+ + + + +++ + + 




. r r'jU 
."; !i.0Ul 





I " ■;; ' iilQi 

Till ll'UJII 

i 1,1 iii ini 

,f ■ I II II K 
:.rl Hlptt 

hiiaiM 

j,i,I! ii:i:"iii 

i KjOiiOun. 
ii if ' 

iifflnn 

:ruiVui.i! 

[inciiiicii 

•if - 



j ' * ~~i "7". iraESCT^Jen=>'.jr-3i.-.T.-:js'; 

I ni 1 ■. be-- jKaEJ®r.^na®£3aac 



■,~, £3 K 



1/ 



in [J ■ ! \ t ^ 
r '^n:Jii" v :' • : -: ^. ... 



400 

L 



:.c? ? 



Scale, ft 



800 

J 



1,200 

I 



FIGURE 11.— Subsidence-monitoring network. 



14 



Standard traverse surveying procedures 
and equipment, described in a later sec- 
tion, were used to locate the monument 
positions. 

MONUMMENT SPACING 

The network layout was designed with 
monuments spaced at 100-ft intervals. 
Topography, vegetation, and localized 
soil conditions dictated the actual loca- 
tion of each monument, thus final spacing 
ranged from 90 to 100 ft. The spacing, 
which varies between 0.07 to 0.13 times 
the overburden depth, is larger than the 
0.05 recommended by the National Coal 
Board (NCB) Subsidence Engineers' Hand- 
book (6). However, closer spacing was 
considered excessive in the rugged ter- 
rain. The larger spacing was sufficient 
to provide the required data, while also 
reducing monument installation and sur- 
veying costs. 




MONUMENT CONSTRUCTION 

Two different types of subsidence mon- 
uments were installed at the Price River 
study site. Initially, 1-1/2-in steel 
pipes, beveled on one end to ease instal- 
lation, were installed over panel 4E. 
The remainder of the monitoring net- 
work was completed using 1-in steel rods 
with machined points. Monuments were 
installed using a sledge hammer to drive 
the monuments to a depth of 5 ft or 
until refusal (fig. 13). The 1-in steel 
rods are recommended because they are 
easier to store, transport, and install, 
and they are less expensive. Monuments 
of both types, which were located over 
stable ground, were monitored for 
the duration of the study. Statistical 




>- • r*- 



t^ 



Mikm 



FIGURE 12.— Access to site limited by heavy snows. 



FIGURE 13.— Monument installation using sledge hammer 



15 



analysis of the stable monuments showed 
a standard deviation on monument move- 
ment equal to the standard deviation of 
the surveying method. Therefore, these 
types of monuments provide equal sta- 
bility for subsidence monitoring in these 
conditions. 

MONITORING PROCEDURES AND EQUIPMENT 

Traverse surveys were used to measure 
both vertical and horizontal displace- 
ments. The surveys were performed by 
Bureau personnel and a contract surveyor 
using a second-order, optical-reading 
theodolite with micrometer readings of 
1 s and an electronic distance-measuring 
(EDM) instrument with an accuracy of 
±0.02 ft +6 ppm (fig. 14). Vertical and 
horizontal positions of each subsidence 




monument were calculated from horizontal 
and vertical angles and slope distances 
measured from instrument stations with 
known coordinates. 

The target-prism unit used for the 
traverse surveys is shown on figure 15. 
The unit consists of a prism for dis- 
tance measurement, a target for angle 
measurements, and a level bubble for 
vertical alignment. The interchangeable 
bottom clamp can be attached to circu- 
lar monuments ranging in diameter from 
9/16 to 1-1/2 in. The compact, light- 
weight unit was ideal for carrying in the 
rugged terrain. If additional height was 
required for improved visibility, 1-ft 
aluminum extensions were attached between 
the clamp and the target. 

Survey accuracy was determined from 
coordinate data collected from subsidence 
monuments located on stable ground at 
the study site. The average standard 




FIGURE 14.— Theodolite with electronic distance meter. 



FIGURE 15.— Target-prism unit. 



16 



deviations for the eastings, northings, 
and elevations, were 0.16, 0.12, and 0.07 
ft, respectively. 

DATA PROCESSING 

Following each traverse survey, field 
data were typed into computer files and 
stored. The raw survey data entered into 
these files consisted of station names, 
horizontal and vertical angles, slope 
distances, and target and instrument 
heights. The easting, northing, and ele- 
vation of each subsidence monument was 
then computed and stored in a mass stor- 
age file; this file was segregated 
according to individual surveys. In this 



form, the information was readily ac- 
cessed and used as input for programs 
that performed calculations such as coor- 
dinate and elevation differences between 
any two surveys. The data were also used 
for mapping monument locations and plot- 
ting subsidence profiles. 

Computation and storage requirements 
for a project of similar size and nature 
could be satisfied by a desk-top 16- 
bit microcomputer with printer and disk 
drive. Approximately 250,000 bytes of 
disk storage would be required, depending 
upon the exact amount of data being 
manipulated. Graphics capabilities would 
require the addition of a plotter and 
graphics software. 



SUBSIDENCE RESULTS 



The final longitudinal subsidence pro- 
files for panels 4E and 5E are shown 
on figures 16 and 17. (See appendix 
for data. ) A transverse monitoring line 
was installed across panels 4E and 5E; 
however, owing to the limited face ad- 
vance in both panels, the transverse 
monitoring line was not undermined, and 
therefore no transverse subsidence pro- 
file was obtained. Without the informa- 
tion from a transverse monitoring line, 
the surface effects of the chain pillars 
between panels 4E and 5E could not be 
determined. 

The maximum subsidence measured over 
the two panels was 2.2 ft, located near 
the midpoint of panel 4E at station C21; 



2.2 ft is approximately 37 pet of the 
average extraction height of 5.9 ft. The 
maximum subsidence measured over panel 5E 
was 1.7 ft at station D20. 

Using an average overburden depth for 
each panel, the width-to-depth ratios 
for panels 4E and 5E were calculated to 
be 0.4 and 0.5, respectively. A higher 
width-to-depth ratio usually results in a 
higher value of subsidence when the ratio 
is subcritical. However, at this site, a 
larger maximum subsidence was measured 
over the panel with the lower width- 
to-depth ratio. The subsidence value 
over panel 4E probably was greater than 
that over panel 5E because of the con- 
tributory effects of the adjacent mining 



o 

-.5 
-1.0 
-1.5 
-2.0 
-2.5 



1 1 1 

r i C6 

,' — ^v C JJ C i 6 


i 

C21 


1 1 1 
C26 C3I C36 C40 


V 

\ 

V 




/ 


\ 
\ 
\ 
\ 

V 

I 




/ 

6 


\ 
\ 

\ 




1 
1 
1 
1 
1 
1 
s 
/ 
/ 


KEY " 




- 


a Before subsidence 
o Final measured subsi 
V/A Unmined coal 

Pnnpl 


Jence 

4E 

1 


6/17/81 


'//////////////A 


, V////////////////////A 



4E. 



500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 

DISTANCE, ft 

FIGURE 16.— Final longitudinal subsidence profile for panel 



0.5 



-.5 

8" -i.o 

z 

LU 
Q 

w -I.5 

oo 

=) 

IT) 

-2.0 



-2.5 - 



I 

Dl D6 


r i 

DM DI6 


— r~ 

D2I 


I - I I 

D26 030 D35, ,D40 


} ^D» 


v ----c^ v 






- 


\ 
\ 
\ 




r- '"''' 




\ 




1 

6 




*J 




i 


- 


KEY 


.P"' 


i 


a 


Before subsidence 




- 


o 


Final measured subsidence 


6/17/81 


sa 


Unmined coal 




_ 




Pani 


il 5E 

I 




W///AW//A \ 


V//////////////A 



5E. 



500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 

DISTANCE, ft 

FIGURE 17.— Final longitudinal subsidence profile for panel 



17 



in panels 2E and 3E (fig. 8). There was 
no mining adjacent to panel 5E other than 
panel 4E. 

The surface ground strain associated 
with mine subsidence was not monitored at 
this site. However, figure 18 provides 
visual evidence that significant surface 
strain was present. The effects of this 
strain are illustrated by the tension 
cracks in this surface structure located 
near subsidence monument D26 over panel 
5E. 

The progression of subsidence over pan- 
els 4E and 5E is shown in figures 19 
and 20. (See appendix for data. ) Sub- 
sidence was first detected over panel 
4E in October 1979 (fig. 19) after the 
longwall face had retreated 1,450 ft, 



approximately 100 ft short of the final 
panel length of 1,550 ft. At this time, 
a maximum subsidence of 0.6 ft was mea- 
sured at stations C20 and C2 1 . The July 

1979 survey showed no subsidence; there- 
fore, subsidence initially began over 
panel 4E between July and October of 
1979, during which time the length of the 
mined panel was between 1,180 and 1,450 
ft. 

Panel 4E was next surveyed in August 

1980 after panel 5E had retreated 1,250 
ft. The maximum subsidence over panel 
4E increased to 1.3 ft at stations 
CI 9, C20, and C21. Subsidence contin- 
ued to increase over panel 4E until June 
1981, at which time panels 4E and 5E 
had been completed for 19 months and 




FIGURE 18.— Damage to surface structure located over 
panel 5E. 



0.5 

-.5 
-I.0 
-I.5 
-2.0 
-2.5 



e^em% 



—r- 

C6 



Cll 



C2I 



C26 



C3I C36 C40 

\ Ik .-j/r- X 



W/7 

KEY \ V^ J I 

a Before subsidence ^~\ / 

o 10/ 16/79 \ / 

A 8/18/80 V^ / 

+ 6/17/81 final V 

Y/A Unmined coal 

Panel 4E 



\y///////////////A 



V/////////////////A 



500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 

DISTANCE, ft 

FIGURE 19.— Subsidence development profiles for panel 4E. 



0.5 



-.5 

UJ 

u -I.0 

z 

UJ 
Q 

c/> -1. 5 
m 

3 
en 

-2.0 
-2.5 



^•<s:x- 



Dl 06 



DM 



DI6 D2I D26 D30 D35 D40 



^ 



\ 



KEY \ v "\/ r ' / 

o Before subsidence \ . — 
o 8/I8/80 v " 

A II/4/80 
+ 6/I7/8I final 
Y/A Unmined coal 






/-^^ 



Y/////////////A, 



Panel 5E 



W/////////////A 



500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 

DISTANCE, ft 

FIGURE 20.— Subsidence development profiles for panel SE. 



18 



6 months, respectively. Subsidence in- 
creased from 0.6 ft to a maximum of 
2.2 ft following the completion of both 
panels. 

Subsidence was first detected over pan- 
el 5E in August 1980 (fig. 20). At this 
time, the 5E longwall face had retreated 
1,250 ft, and the maximum subsidence was 
approximately 0.9 ft at several stations 
over the center of the panel. The monu- 
ments over panel 5E were stable when 
surveyed in June 1980. Initial subsid- 
ence movements were not detected until 
August 1980, which indicates that subsid- 
ence began between June and August 1980 
when the length of the mined 5E panel was 
between 950 and 1,250 ft. The final 
survey of 1980 was performed in November; 



the face had retreated 1,800 ft, and 
the maximum subsidence was 1.4 ft at 
station D20. Mining was completed in 
panel 5E during December 1980; length of 
the final panel was 1,950 ft. 

Subsidence continued to increase over 
panels 4E and 5E until June 1981. Upon 
completion of panel 5E , subsidence had 
increased over 5E from approximately 1.5 
ft to its final maximum of 1.7 ft. 

A survey in June 1982 showed that no 
further subsidence had occurred over any 
part of the subsidence-monitoring net- 
work. The surface had remained stable 
for 1 yr; this indicates that without 
further mining in the area, the surface 
would probably remain stable with no 
significant additional subsidence. 



CONCLUSIONS 



The Price River Coal Co. No. 3 Mine 
study site is located in an area where 
the only present and reasonably forsee- 
able future land uses are for domestic 
cattle grazing, for forestry, and as a 
wildlife habitat. Theoretically, subsid- 
ence effects that might alter these land 
uses include decreased surface stability, 
such as slope failure and surface fis- 
sures, and altered drainage patterns. 
Surface instability could endanger live- 
stock and wildlife, and altered drainage 
patterns might adversely effect the vege- 
tation, which is the food supply for 
grazing animals, and the trees, which 
might be harvested for timber. At this 
site, the entire surface area affected by 
subsidence was approximately 65 acres. 
Within the study area, no ground sur- 
face damage was detected, and the sur- 
face remained stable with no indications 
of slope failure or surface fissures. 
Because there were no significant ef- 
fects on the original topography, no 



noticeable changes to the local drain- 
age patterns were observed. Overall, the 
physical effects on the surface were 
negligible except for the damage caused 
to the abandoned surface structure (fig. 
18). However, there was no diminution 
of value or forseeable use of the 
land. 

Although the data from this report by 
itself cannot be used to predict subsid- 
ence, it does provide some insight as to 
the magnitude of subsidence that can be 
expected from longwall mining within the 
Book Cliffs Coalfield. Using these data 
in conjunction with data obtained from 
other Western U.S. subsidence studies, 
existing subsidence prediction methods 
can be validated or modified, or new 
methods can be formulated for similar 
geologic conditions. These prediction 
methods in turn can be used to improve 
the design of mines to help prevent 
or limit the adverse effects of mine 
subsidence. 



REFERENCES 



1. HRB-Singer, Inc. (State College, 
PA). The Nature and Distribution of Sub- 
sidence Problems Affecting HUD and Ur- 
ban Areas (Task A) (U.S. Dep. Housing 
and Urban Dev. contract H-2385). 1977, 
113 pp.; NTIS PB 80-172778. 



2. Mining Informational Services. 
1983 Keystone Coal Industry Manual. 
McGraw-Hill, 1983, 1388 pp. 

3. U.S. Geological Survey. Standard- 
ville 7.5-Minute Quadrangle Map N3937.5- 
W11052.5/7.5, 1914. 



19 

4. Utah State Climatologist . Scofield Book. Cliffs, and Emory. UT Geol. and 
Dam Weather Station, UT State Univ., Miner. Survey Monogr. Ser. No. 3, 1972, 
Logan, UT. Private communication, 1983; 571 pp. 

available upon request from A. J. Fejes, 6. National Coal Board. Subsidence 

BuMines, Denver, CO. Engineers' Handbook. 1975, 111 pp. 

5. Doelling, H. H. Central Utah Coal- 
fields: Sevier-Sanpete, Wasatch Plateau, 



20 



APPENDIX. —MEASURED SUBSIDENCE VALUES PLOTTED IN FIGURES 16, 17, 19, AND 20 





Base 

elevation, 

ft 


Elevation c 


if f erences 


by date 




Station name 


10/16/79 


8/18/80 


9/15/80 


11/4/80 


6/17/81 


CI 


6,828.01 
6,854.45 
6,914.26 
7,000.90 
7,088.49 
7,167.34 
7,301.14 
7,374.97 
7,306.67 
7,203.63 
7,054.31 
7,021.36 
6,948.47 
6,947.43 
7,038.78 
7,095.94 
7,221.24 
7,322.60 
7,262.96 
7,219.53 
7,065.85 
6,964.41 
6,898.31 
6,841.36 
6,779.57 
6,749.90 
6,726.74 
6,732.30 
6,801.98 
6,885.23 
6,951.60 
7,020.16 
7,080.27 
7,139.50 
7,265.63 
7,292.71 
7,334.50 
7,327.85 
7,341.89 
7,299.24 


-0.03 

-.15 

-.23 

-.19 

-.16 

NS 

NS 

.11 

-.03 

-.04 

-.07 

-.12 

-.07 

.14 

.10 

.35 

.38 

.52 

.51 

.62 

.57 

.43 

.37 

.40 

.14 

.00 

.04 

-.01 

.01 

-.01 

.06 

-.08 

.03 

NS 

.00 

.04 

-.02 

.01 

-.02 

.06 


0.01 

-.12 

NS 

NS 

NS 

.13 

-.07 

NS 

NS 

NS 

-.14 

-.15 

NS 

NS 

.51 

NS 

.98 

NS 

1.27 

1.33 

1.34 

1.24 

NS 

.71 

.45 

.21 

.02 

-.06 

.03 

NS 

-.01 

.09 

.15 

.26 

NS 

-.02 

-.06 

-.05 

-.05 

-.06 


0.04 

-.01 

-.07 

NS 

-.11 

-.11 

.02 

.02 

.23 

.38 

.27 

.30 

NS 

1.00 

1.11 

NS 

1.50 

1.90 

1.86 

1.95 

1.93 

1.81 

NS 

1.38 

.87 

.59 

.41 

.16 

.27 

NS 

.13 

.10 

.23 

.21 

NS 

.18 

-.03 

.07 

.11 

.09 


0.01 

-.12 

-.16 

NS 

-.05 

.04 

.10 

NS 

.11 

NS 

.14 

.19 

NS 

NS 

1.07 

NS 

1.50 

NS 

1.82 

1.92 

2.03 

1.85 

NS 

1.46 

.97 

.69 

.34 

.24 

.28 

NS 

.11 

.05 

.25 

.25 

NS 

.12 

.07 

.10 

.07 

.07 


0.00 


C2 


- .09 


C3 

C4 

C5 

C6 


-.14 
-.11 
-.09 
- .17 


C7 

C8 

C9 


-.04 
.04 
.08 


CIO 


.14 


en 


.11 


C12 


.09 


C13 


.43 


C14 


.79 


C15 


.99 


C16 


1.41 


C17 


1.53 


C18 


1.76 


C19 


1.95 


C24 


2.02 
2.16 
2.00 
1.73 
1.56 


C25 


1.13 


C26 


.87 


C27 


.29 


C30 


.31 

.30 

NS 


C31 

C34 


.23 
.06 

.14 
.20 


C35 

C38 


NS 
.09 
.11 
.13 


C39 


-.05 




.17 



21 



APPENDIX.— MEASURED SUBSIDENCE VALUES PLOTTED IN FIGURES 16, 

17, 19, AND 20— Continued 



Station name 



Base 

elevation, 

ft 



Elevation differences by date 



10/16/79 8/18/80 n 9/15/80 11/4/80 



6/17/81 



Dl 

D2 

D3 

D4 

D5 

D6 

D7 

D8 

D9 

D10 

Dll 

D12 

D13 

D14 

D15 

D16 

D17 

D18 

D19 

D20 

D21 

D22 

D23 

D24 

D25 

D26 

D27 

D28 

D29 

D30 

D31 

D32 

D33 

D34 

D35 

D36 

D37 

D38 

D39 

D40 

NS Not surveyed. 



663.67 
726.40 
791.59 
860.30 
932.03 
005.21 
024.23 
015.01 
959.44 
897.17 
825.09 
753.45 
676.13 
715.63 
780.40 
855.56 
898.49 
863.46 
846.90 
818.67 
809.14 
784.63 
769.45 
726.87 
648.88 
646.24 
684.22 
711.33 
723.35 
748.45 
776.52 
804.00 
827.17 
841.32 
886.00 
897.76 
898.34 
890.85 
849.04 
876.73 



NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 
NS 



•0.01 
.04 
-.03 
-.01 
.04 
.12 
-.08 
.09 
.13 
.14 
.20 
.24 
.48 
.57 
.87 
.83 
.94 
.93 
.86 
.88 
.61 
.52 
.42 
.40 
.31 
.34 
.29 
.30 
.31 
.16 
.14 
.21 
.13 
.08 
.00 
.02 
-.02 
-.05 
.00 
.00 



0.04 

.02 

.00 

.01 

.04 

-.04 

.01 

.04 

.17 

.16 

.15 

.18 

.47 

.64 

.85 

.95 

1.10 

1.13 

1.17 

1.22 

.97 

.80 

.69 

.46 

.40 

.28 

.26 

.17 

.30 

.14 

.20 

.26 

.15 

.02 

-.02 

-.09 

.03 

-.02 

-.01 

.07 



0.04 

.02 

.04 

.04 

.08 

.11 

.14 

.08 

.09 

.17 

.19 

.24 

.49 

.69 

.67 

1.05 

1.23 

1.30 

1.30 

1.44 

1.30 

1.21 

.88 

.87 

.72 

.49 

.40 

.31 

.33 

.25 

.27 

.25 

.12 

.06 

.01 

-.01 

.03 

.01 

-.02 

.01 



.08 

.01 

.02 

.03 

.07 

.00 

.00 

.06 

.14 

.13 

.12 

.11 

.51 

.82 

.97 

1.09 

1.34 

1.46 

1.59 

1.73 

1.60 

1.56 

1.50 

1.42 

1.28 

.88 

.63 

.42 

.42 

.33 

.28 

.38 

.10 

.11 

.02 

-.07 

.05 

-.03 

-.05 

.06 



NOTE. — A negative value denotes an upward ground movement. 



6 U.S. GOVERNMENT PRINTING OFFICE: 1986—605-017/40,075 



I NT ,-BU .OF Ml NES,PGH ,,PA . 28351 



78, 



U.S. Department of the Interior 
Bureau of Mines-Prod, and Distr. 
Cochrans Mill Road 
P.O. Box 18070 
Pittsburgh. Pa. 15236 

OFFICIAL BUSINESS 
PENALTY FOR PRIVATE USE. $300 

| | Do not wi sh to receive thi s 
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from your mailing list* 

| | Address change. Please 
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AN EQUAL OPPORTUNITY EMPLOYER 





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